An entertaining gross-out, cautionary tale, tyro director Morgan Spurlock’s “Super Size Me” personalizes the warnings in runaway bestseller “Fast Food Nation” by submitting the filmmaker himself to a diabolical experiment: For 30 days he eats only from McDonald’s menu. The havoc this wreaks on a hitherto athletically fit body will have most viewers running for the nearest salad bar. While docu’s slight air of “reality TV” stuntdom and self-promotion make it seem most suitable for TV, its standout popularity with Sundance auds suggest sleeper arthouse success — though any distrib concerned about fast-food tie-in deals should pass on this one.

Affable, amusing and attractive in an average-Joe-post-college way, Manhattan resident embarks on his high-caloric, low-nutritional value odyssey after first getting checked out by a battery of doctors and nutritional experts. Finding him in the pink of health, they’re not too concerned about his curious plan — though that changes radically as the diet’s fast-developing harms (in some ways commensurate to acute alcoholism) take hold.

One party concerned from the start is protag’s girlfriend, who’s appalled by the scheme (she’s a vegan chef).

To further heighten the worst-case-scenario potentialities, Spurlock must answer yes every time a McD’s employee asks him “Do you want that Super Sized?” — which translates to 42 ounces’ sugar-loaded soda and a half-pound of fries on top of whatever fatty entree he’s ordered. He also commits to exercising no more than the American average — which amounts to little more than walking a mile per day.

From his first, regurgitation-producing attempt to finish a “Super Sized” meal to the final weigh-in, docu leaves little doubt that eating this stuff on a regular (or even occasional) basis is bad, bad, bad for ya. Spurlock gains weight and suffers asthma, chest pains, depression, headaches, sugar/caffeine crashes and heart palpitations. His cholesterol level skyrockets and his liver grows clogged with fat; he gains 25 pounds. By the third week, his shocked medical consultants are basically telling him that his life is in his own hands.

Super-gross as much of this is (including a peek at increasingly popular “obesity surgery”), tenor is primarily humorous in a believe-it-or-not fashion. Traveling the country during his ordeal, Spurlock interviews scholars, “Diet for a New America” author (and Baskin-Robbins ice cream heir) John Robbins, former surgeon general David Sacher, Subway weight-reduction poster boy Jared Fogel, some miscellaneous fast-food freaks and numerous people on the street. McDonald’s execs, however, fail to return his many calls.

While not the all-encompassing, hard-facts indictment “Fast Food Nation” readers might hope for, this more entertainment-oriented package does throw in enough disturbing figures (300,000 Americans die each year of obesity-related conditions) and informative side trips to provide an educational-value meal. It’s noted that most U.S. school cafeterias are now supplied by food corporations whose prepackaged, heavily processed items are scarcely healthier than what’s available at the drive-up window. Significantly, one such institution that switches to a healthier menu witnesses a drastic reduction in behavioral problems — and it’s a school for troubled kids.